544 



SCIENCE 



[N. S. Vol. XLIII. No. 1111 



are cordially invited to attend both lecture and 

 conversazione. No cards are necessary. 



TDESDAT, APRIL 18 



Morning Session 

 10:30-12:45 a.m. — Auditorium, National Mu- 

 seum. Public scientific session for the reading of 

 papers. 



Some Seoent Sesults of Solar Besearch: George 

 E. Hale. 



The new results include photographs and stereo- 

 grams of the solar atmosphere made with a 13- 

 foot spectroheliograph ; part of a new map of the 

 snn-spot spectrum, on a scale of one centimeter to 

 the angstrom, showing the magnetic phenomena of 

 sun-spots; illustrations of the Stark effect for 

 hydrogen and lithium; and observations indicating 

 that the northern and southern sun-spots of the 

 present cycle, irrespective of latitude, are oppo- 

 site in magnetic polarity to the corresponding 

 spots of the preceding cycle, while the chromo- 

 spherio vortices associated with spots did not 

 undergo a similar reversal in sign at the minimum. 

 An Investigation of the Suggested Mutual Re- 

 pulsion of Fraunhofer Lines: Chakles E. St. 

 John (introduced by G. E. JBLale). 

 Those who assign an important rOle to anoma- 

 lous dispersion in the solar atmosphere deduce 

 from tlie theory a mutual influence between the 

 components of close pairs of Fraunhofer lines, 

 which operates to increase their distance apart. 

 Investigations now nearing completion show that 

 the relative positions of lines in close solar pairs 

 conform to their relative positions in terrestrial 

 spectra to the same degree of precision as free- 

 standing solar lines which are not under the in- 

 fluence of neighboring lines, and the violet and red 

 components are not displaced to the violet and red 

 respectively as the theory demands that they 

 should be in the solar spectrum. 

 Anomalous Dispersion Phenomena in Electric Fur- 

 nace Spectra: Arthur S. Kins (introduced by 

 G. E. Hale). 



Strong anomalous dispersion effects have been 

 produced by passing white light through metallic 

 vapors in an electric furnace. A study under high 

 dispersion of spectrum lines very close together 

 gave no indication of the mutual repulsion pre- 

 dicted by Julius when one of the lines in question 

 shows high anomalous dispersion. Other experi- 

 ments, in which the wave-length of a line was 

 measured when alone and also when very close to 

 a strong line of another element, gave no difference 

 greater than 0.001 angstrom. 



Illustrations of the New Spectroscopic Method of 

 Measuring Stellar Distances: Walter S. Adams 

 (introduced by G. E. Hale). 

 The method of determining the actual light emis- 

 sion of a star from the appearance of the absorp- 

 tion lines in its spectrum has proved a valuable 

 way of measuring stellar distance, since the dif- 

 ference between the actual and apparent bright- 

 ness of a star depends only on its position in space. 

 The new method has been used to determine the 

 distance of a remarkable pair of faint stars in the 

 southern sky, showing that the components move 

 in parallel paths at the greatest known stellar ve- 

 locity — about 600 km. a second. Another interest- 

 ing application relates to the total light emission 

 of the sun. By simply comparing the relative in- 

 tensities of five lines in the solar spectrum the 

 apparent brightness can be estimated with an ac- 

 curacy comparable with that of direct photometric 

 measurement. 



Some Results with the New 10-inch Fhotographic 

 Telescope: Harlow Shaplet (introduced by 

 G. E. Hale). 



The new Cooke photographic triplet of 10 inches 

 aperture, focal length 45 inches, has been used 

 with a 15-degree objective prism to photograph 

 spectra of faint stars. The scale is three minutes 

 of arc to the millimeter and a single plate covers 

 nearly 400 square degrees. As many as 10,000 

 spectra have been photographed at one exposure. 

 The instrument has been applied to the study of 

 Cepheid variables, and the spectra of about a 

 dozen have been found to vary periodically with 

 the light. 



The Fyranometer, an Instrument for the Measure- 

 ment of STcy Radiation: C. G. Abbot and L. B. 

 Aldrich. 



The authors have perfected an instrument to 

 measure the radiation originally forming a part of 

 the beam of rays from the sun, but which reaches 

 the observer by scattering from all parts of the 

 sky. The instrument can also measure the radia- 

 tion outward toward the sky and space at night, 

 comprising those long wave-length radiations which 

 are purposely excluded in the daylight measure- 

 ments. For the first purpose the instrument is 

 provided with an optically figured hemispherical 

 shell of ultra-violet crown glass about 2 mm. 

 thick. The diameter of the shell is about 25 mm. 

 For nocturnal radiation measurements this shell 

 is not employed. The horizontal measuring sur- 

 face is a thin blackened strip of manganin about 



